The present invention relates to drainage field systems and, more particularly, to chamber leach line systems which are manufactured and ready to install in a drainage field for wastewater and stormwater.
Residential septic tank systems are used where municipal sewerage systems are not available. Wastewater from the home flows into the septic tank for on-site treatment through the biological activity of microorganisms, and leachate passing from the septic tank flows into a drain field from which it percolates into the ground. Drain fields of standard construction include a network of trenches dug in the ground, with a layer of loose aggregate material, such as gravel, placed in the bottom of the trench. A pipe is connected to the outlet of the septic tank and also connected to perforated pipes which are laid into the network of trenches. The space between the perforated pipe and the ground, which is filled by the loose aggregate, essentially becomes a drainage cavity for receiving leachate discharged through the perforations in the pipe. In normal operation, the septic tank effluent flows out into the network of perforated pipes and slowly percolates through the aggregate in the bottom of the trenches and down through the soil. Standard systems such as the one described are not well adapted for handling peak flows, such as might be experienced when several high volume water consumption activities are occurring simultaneously in the house, or when the leaching field is intended to handle stormwater.
Chamber-type drainage systems are able to handle larger flows and have become more widely used as an improvement over standard systems. A chamber system includes a void space into which excess effluent can flow for holding prior to percolation through the ground. The chambers are generally buried in a network of trenches as part of the leach field system. Chamber systems thus provide the advantage of being able to accommodate larger peak flows of effluent than standard systems. Examples of such chamber systems include U.S. Pat. No. 5,511,903 to Nichols et al., U.S. Pat. No. 5,498,104 to Gray, U.S. Pat. No. 5,017,041 to Nichols, and U.S. Pat. No. 4,759,661 to Nichols et al. Even though chamber systems accommodate larger peak flows, however, leaching chambers systems have not achieved the soil interface characteristics offered by conventional trench and gravel installations.
With the foregoing in mind, the present invention advantageously provides a chamber unit for leaching effluent in a leach field. An embodiment of the chamber unit comprises a chamber cavity for therein receiving effluent for leaching, at least one panel positioned to define a periphery of the chamber cavity, and aggregate comprising a plurality of bodies positioned adjacent the panel for filtering effluent. The aggregate may be conventional gravel but is preferably a lightweight particulate material such as expanded polystyrene, polyethylene, polyurethane, polypropylene, and rubber chips such as obtained from ground up tires.
In a preferred embodiment of the invention chamber units are fluidly connected together and to a source of effluent to thereby form a chamber leach line. A sufficient number of leach lines is then positioned in trenches excavated in soil to form a leach field. A chamber unit may be connected to a source of effluent so as to receive effluent directly into the chamber cavity. The soil floor of the excavated trench generally forms the lower periphery of the chamber leach line, through which effluent filters into the soil. It is known that the soil surface through which effluent filters will generally develop a film of microbial growth, a biofilm which may eventually clog the soil surface. Advantageously, aggregate may be positioned relative to the chamber unit cavity so as to filter effluent flowing out of the chamber cavity and into the surrounding soil of the trench. The aggregate material provides a greatly increased surface area for biofilm accumulation, which in turn serves for enhancing microbial treatment of the effluent to thereby reduce nutrients leaching into the soil.
A further embodiment positions aggregate along side peripheries of the chamber cavity, so that effluent is filtered through the aggregate as it flows laterally out of the chamber cavity and into the surrounding soil. Aggregate, however, may also be positioned along a lower periphery of the chamber cavity to provide filtration for effluent flowing downwardly from the cavity into the soil of the trench. Aggregate positioned along side peripheries of the chamber cavity is preferably contained in a sleeve of water permeable material, and may be thus prefabricated prior to field installation. Under normal flow conditions, effluent generally flows into the surrounding soil through the lower periphery of the chamber cavity. Under excess flow conditions, however, where the soil underlying the chamber cavity is unable to absorb the volume, effluent will also flow laterally into the surrounding soil through side peripheries of the chamber cavity, thereby being filtered through the aggregate.
In another embodiment, side peripheries of the chamber cavity are defined by perforated conduit connected to a source of effluent so that the effluent passes through the conduit and trickles into the chamber cavity from the perforated conduit. This embodiment may have aggregate positioned adjacent the perforated conduit so as to filter effluent trickling from the conduit into the chamber cavity.
In yet another embodiment the chamber unit includes a plurality of foldingly connected, substantially flat panels positioned to define peripheries of a chamber cavity when properly positioned unfolded in a trench excavated in a leach field. This embodiment includes at least one conduit positioned to deliver effluent to the chamber cavity. Prefabrication of the chamber unit as a plurality of connected substantially flat panels which advantageously fold along the connections for allowing easy storage and transportation of the units in a folded position. Additionally, the individual units are easily set up by unfolding and properly positioning within trenches to thereby form chamber leach lines when connected together.
The invention further includes a leach field for leaching effluent into soil. The leach field comprises a source of effluent, a plurality of trenches excavated in soil adjacent the source of effluent, and a plurality of leach lines positioned in the plurality of trenches in fluid connection with the source of effluent for distributing the effluent by leaching into the soil. Each leach line of the plurality includes at least one chamber unit comprising a cavity for therein receiving the effluent for leaching, at least one panel positioned along a periphery of the cavity, and an aggregate comprising a plurality of bodies positioned adjacent the panel for filtering effluent.
A method aspect of the invention includes leaching effluent into a leach field by conducting effluent from a source of effluent to a chamber for holding prior to leaching, filtering the effluent through an aggregate as the effluent flows from the chamber, and leaching the effluent into the leach field after filtering through the aggregate. A further embodiment of the method comprises conducting effluent from a source of effluent, filtering the effluent while the effluent flows into a chamber for holding prior to leaching, and leaching the effluent from the chamber into the leach field.
The invention additionally includes a method of constructing a leach field for effluent. This method comprises excavating a plurality of trenches in soil, positioning a plurality of panels in the trenches so as to define a plurality of walls for chamber leach lines, positioning aggregate adjacent the plurality of panels for substantially filtering the effluent leaching into the field, and connecting the aggregate chamber leach lines to a source of effluent.